Connection system for magnet excitation coils



2 She ets-Sheet 1 March 21, 1967 R. A. KILPATRICK CONNECTION SYSTEM FORMAGNET EXCITATION COILS Filed July 13, 1965 INVENTOR ROBERT A.KILPATRICK ATTORNEY.

March 21, 1967 R. A. KILPATRICK 3,310,764

CONNECTION SYSTEM FOR MAGNET EXCITATION COILS Filed July 13, 1965 2Sheets-Sheet 2 A L A \k INVENTOR ROBERT A. KILPATRICK ATTORNEY.

United States Patent 3,310,764 CONNECTION SYSTEM FOR MAGNET EXCITATIONCOILS Robert A. Kilpatrick, Orinda, Calif., assignor to the UnitedStates of America as represented by the United States Atomic EnergyCommission Filed July 13, 1965, Ser. No. 471,774 9 Claims. (Cl. 335213)The present invention relates to charged particle accelerators and moreparticularly to an improved Winding arrangement for the magnetexcitation coils of particle accelerators of the type having a series ofmagnet sections spaced along the beam orbit thereof.

In particle accelerators such as the alternating gradient or so-calledstrong focussing proton synchrotron, the charged particles are directedalong a closed path and the particle beam is confined to the desiredbeam envelope by means of a continuous series of alternate focussing anddefocussing magnet sections which present opposite transverse magneticfield gradients to the beam. This method of beam control has proven veryadvantageous, as will hereinafter be discussed, and may be used onlinear as well as closed orbit machines. The invention will be describedwith reference to circular machines sinceit was initially designed foruse in this context.

The magnets for the focussing and defocussing sections are C-shaped incross-section and essentially act as corresponding halves of aquadrupole. The magnets are disposed in a regularly alternatingarrangement around the beam path with the spaced pole faces forming avertical gap through which an elliptical beam aperture is defined. Thepole faces of the focussing magnet sections diverge radially inward withrespect to the beam orbit and thus the magnetic field strength acrossthe gap increases in the radially outward direction. The pole faces ofthe defocussing magnet sections diverge radially outward and themagnetic field strength in these regions increases in a radially inwarddirection. This systematic reversal of the field gradients providesopposing alternate restoring forces to the beam whereby the particlesare deflected radially inward during focussing and radially outwardduring dcfocussing. Similar to lens action in optics, the magnetsections perform alternate opposite convergences in the vertical plane,thereby confining the beam to the desired aperture size.

The alternating gradient concept of orbital stability has I led tosignificant economies in accelerator design. The strong focussingdecreases the free oscillation amplitude of the particles therebyreducing the necessary beam aperture and substantially reducing thenecessary magnet size for a given energy. The amount of magnet steel maybe reduced by a factor of 100 from that required for comparable weakfocussing magnets. An improved momentum compaction factor reduces thenecessary dimensions of the pole faces to further reduce the magnetsize, as well as reducing the energy stored in the field and the powerrequired for excitation. It therefore becomes practical to cycle themagnets at much higher frequencies, thereby increasing the number ofbeam pulses per second and the time-average intensity of the beam.Consequent- 1y machines of much higher energies become feasible.

Due to the unavoidable limitation imposed by the magnetic permeabilityof iron, the increase in the maximum energy of these machines must beaccompanied by an increase in the beam orbit radius. In fact, thealternating gradient technique itself requires a larger radius for agiven energy due to a need for many fieldfree spaces between thefocussing and defocussing sectors. Thus the more advanced machinedesigns are running to larger and larger orbital dimensions. Forexample, a 200 bev.

3,310,764 Patented Mar. 21, 1967 proton synchrotron is currently beingdesigned. The subject invention was developed for this machine whichwill use 504 focussing and defocussing magnet sections arranged aroundan orbit approximately one mile in diameter.

Successful application of the alternating gradient concept requiresnearly perfect beam-guiding fields within the magnet, and as themachines get larger the degree of precision required becomes relativelygreater. The flux density precision requirements of the gradient magnetsof the 200 bev. machine, for instance, have been estimated at 0.01%.Such nearly perfect beam-guiding fields thus impose comparable accuracydemands on the magnet excitation coil system and on the alignment of thesuccessive magnet sections.

When dealing with magnets of the size used in these machines, theproviding of magnet excitation windings, which must have a coolantcirculating system incorporated therein, is not a simple technique ofturning a wire around the poles but becomes a major fabricatingoperation in itself. In addition to the field accuracy requirements,practical problems of insulation, capacitance and the like presentfurther difliculties.

The magnet coils are generally made up of layered subassemblies ofessentially rectangular copper conductor. Each layer contains a portionof the turns required for the particular pole, disposed in a singleplane from an outermost turn to an innermost turn. The layers areappropriately interconnected and stacked to form the total coil assemblyfor that pole. In order to have an integral number of turns on a coil,which is necessary for the sake of magnetic field symmetry, bothterminals of the coil assembly occur at the same circumferential pointwith respect to the magnet pole. Thus in the past, the coil terminalshave necessarily been at the same end of each magnet section andconnection between adjacent sections has necessitated bus bars runningparallel to the outside of the magnet section itself. Since the longdimension of the magnet sections lies in the direction of the particlepath, this doubling back represents a significant amount of repeatedconductor length and adds substantially to the power usage.

In elfect, this has required an extra length of conductor at least equalto the circumference of the accelerator. More often, two separatewinding circuits carrying oppositely-directed currents are used on eachmagnet section. This requires two lengths of copper bar essentiallyencircling the circumference of the beam tunnel. In view of theincreasingly greater physical dimensions being considered for suchaccelerators, the'amount of extra copper becomessubstantialapproximately 6 miles of 3 sq. in. conductor would berequired for the proposed 200 bev. machine. In addition to the cost ofthis amount of copper conductor material, these external connectionsmust be accommodated by a larger tunnel cross-section than wouldotherwise be necessary, which in itself represents a significant costincrease in the larger machines.

In view of the'foregoing it is highly desirable to have an improvedmagnet excitation coil design which reduces the accelerator constructioncosts and which simplifies the fabrication and assembly of the numerousmagnet coils.

The subject invention takes advantage of the reduced magnet energyrequirements and the improved power distribution of the alternatinggradient machines to introduce a radical departure from the previousmagnet coil design. The invention enables adjacent magnet windings to becoupled directly end-to-end without sacrifice to the magnetic fieldsymmetry or significantly adding to the insulation problems.

Whereas conventionally each coil has been composed of a single one ofthe two winding circuits used in the machine, the present design employsa partial turn of both circuits on a single coil to make up the requiredintegral number of turns thereon and to lead the windings oil in thedirection of the subsequent coil. The combined Windings aresystematically alternated among the magnets tocompensate for any currentimbalance between the two circuits and the partial turn placement iscritically prescribed to have negligible effect on the aperture field.

It is accordingly an object of this invention to reduce the cost ofcharged particle accelerators, particularly very large machines of thealternating gradient class.

It is another object of this invention to provide an improved magnetexcitation coil design for charged particle accelerators in which thecoils of successive ones of the magnet sections can be connectedtogether at the adjacent ends thereof.

It is a further object of the invention to provide an excitation coildesign and coil connection system for the magnet of a charged particleaccelerator of the synchrotron type which requires no external bus barcoupling between the magnet sections.

It is still another object of the invention to provide a connectionsystem for the magnet excitation coils of a charged particle acceleratorwhich allows a reduction in the size of the accelerator beam tunnel.

It is another object of this invention to provide for direct end-to-endcoupling of successive magnet excitation coils in an alternatinggradient type of charged particle accelerator.

It is a further object of the invention to provide a magnet excitationcoil winding and connection system which is relatively convenient toassemble and install in a strong focussing type of charged particleaccelerator.

The invention, both as to its organization and operation, together withfurther objects and advantages thereof will be best understood withreference to the following specification taken in conjunction with theaccompanying drawing of which:

FIGURE 1 is a plan view showing a portion of an alternating gradientproton synchrotron including several of the individual magnet sections,

FIGURE 2 is a cross-sectional view of a magnet section taken along line22 of FIGURE 1,

FIGURE 3 is a section view taken along line 3-3 of FIGURE 2 showing anexcitation coil winding of one of the magnet sections, and

FIGURE 4 is a schematic diagram of the excitation coil windings andconnections for the series of accelerator magnets of FIGURE 1.

Referring now to FIGURE 1 there is shown one alternating gradientsequence of the accelerator ring 11 of a charged particle accelerator ofthe synchrotron class. As the accelerator is a very large machine, thecurvature of the beam orbit would be barely perceptible in the segmentshown and has therefore been increased in FIG- URE l for purposes ofillustration. Each alternating gradient sequence of the accelerator ring11 includes four long beam-guiding magnet sections 12, 13, 14 and 15,disposed in succession along the tubular charged particle beam vacuumchamber 17. The magnets 12, 13, 14 and 15 are rectilinear, the gradualcurvature of the beam orbit 18 being obtained by a slightly angledplacement of each successive magnet with respect to the preceding one.

As can best be seen in FIGURE 2, the four gradient magnets 12, 13, 14and 15 have a laminated C-shaped core 19 with the pole faces 21 beingsymmetrically divergent away from the magnet center to form an outwardlywidening gap 22. The magnet 19 constitutes one half of a quadruple and,as such, the essentially hyperbolic profile of the pole faces 21provides a uniform magnetic field gradient along both the horizontal andvertical directions of the gap 22. The vacuum tubulation 17 extendsthrough gap 22 and is of elliptical cross-section, with the major axisbeing horizontal, to conform with the ion beam profile.

The first magnet pair 12 and 13 serve as a focussing section to the ionbeam 18 and are disposed with the back legs of the magnet cores 19radially outward on the accelerator ring 11. By virtue of the taperedgap 22, the magnetic field gradient increases outward across the gap inthis section and produces an inward horizontal restoring force on thebeam 18. The second magnet pair 14 and 15 are disposed with the backlegs radially inward on the ring 11 and form a defocussing section tothe beam 18. In this position of the magnets 14 and 15, the fieldgradient is reversed across the gap 22 and produces an outwardhorizontal restoring force to the beam 18. These restoring forces, ofcourse, are superimposed on the main, circumferentially constantbeam-bending field which is provided by both the focussing anddefocussing magnets. The pattern of the two focussing magnets 12 and 13and two defocussing magnets 14 and 15 is continuously repeatedthroughout the accelerator ring 11 to provide the systematicallyalternating magnetic gradient along the charged particle path 18,thereby confining the particle beam to the desired envelope size. Itshould therefore be understood that the remarks herein directed tomagnets 12, 13, 14 and 15 are not limited thereto but pertain to all thealternating gradient magnet sections of the accelerator.

Referring now to FIGURES 2 and 3 together for an understanding of thecoil structure for the magnets 12, 13, 14 and 15, two excitationwindings 23 are shown separately encircling the upper and lower polesrespectively of the magnet core 19. The windings 23 are each composed oftwo coil layers 24, each of which layers 24 is a rigid pre-formedsubassembly, thin enough to be separately inserted through the narrowmagnet gap 22. The coils are formed of a hollow conductor 26 having arectangular cross-section, through the inner passages 27 of whichcoolant liquid is circulated. Insulation 28 is provided between theturns of a coil layer 24 and a ground plane insulation envelope 29encases each layer. The two coil layers 24 are assembled on each magnetpole and are interconnected at the inermost turn by an electricalterminal 31 and a water fitting 32. The placement of terminal 31 and ofouter terminals 30, 33 and 34 for coupling to other coils 23 willpresently be described in connection with the winding pattern of thecoils. The leg of the coils 23 which extends through the center of themagnet cores 19 is known in accelerator art as the coil window and, ascan be best seen from FIGURE 2, this portion of the coil has thegreatest effect on the beam aperture field. The outer portions of theassembled coils 23 are held in a suporting frame 40, mounted by anglemembers 45 to the longitudinal tie bars 50 of the laminar magnet core 19structure. As an indication of the physical proportions and materialquantity involved in such magnet excitation systems, the abovedescribedcoil assemblies 23 exceed 20 ft. in length and approach a weight of 2tons apiece.

Referring now to FIGURE 4, there is shown a schematic diagram of thecoil 23 winding patterns for each of the four magnets 12, 13, 14 and 15.The graphic arrangement of the windings shown in the schematic is meantto represent, as nearly as possible, the spatial arrangement of thecorresponding coils as shown in the view of FIG- URE 1. The windingpatterns for each of the coil layers 24 are shown to lie in separateplanes with the two layers of each coil assembly 23 in verticalproximity. The coil window leg of the windings is indicated in thisfigure by solid encirclements 35, and the particle path 18 is shown inthe space between the paired winding layers for the respective upper andlower poles of the magnets 12, 13, 14 and 15. Coupling terminals betweenthe coil layers 24 of a single magnet are shown in the schematic assolid dots and the coupling terminals between the coils 23 of successivemagnets are shown as open dots.

As was described earlier, the entire accelerator magnet winding circuitis composed of two members, one being the series return circuit of theother, whereby the currents carried therein are oppositely directed andessentially The paths of the twocircuit memequal in amplitude. bers areindicated in the drawing by the solid line 36 and the dashed line 37,respectively. This conventional use of two circuits reduces the totalenergy and coupling between the magnet circuits and the instrumentationwiring. For various reasons, however, such asdistributed current leakagethrough water passages, capacitance losses to ground, or possiblenon-uniform ripple currents, the two circuits do not necessarily balanceexactly. Since the magnetic flux density precision requirements of thegradient magnets are so critical, the geometry of the subject windingpattern is arranged to minimize, or virtually eliminate, the effects ofthe possible current imbalance between the two circuit 36 and 37.

It should be noted that the current direction through the coil windowlegs 35 of the focussing magnet pair 12 and 13, as shown by the arrowheads, flows opposite to the direction of beam path 18 and that of thedefocussing magnet pair 14 and 15 flows parallel to the beam path, asrequired by the accelerator design. Therefore, .the winding pattern ofthe to oppositely-directed current circuits 36 and 37 as used throughoutboth the focussing and defocussing magnet sections must, first of all,satisfy this condition. The imposed condition of the improved windingpattern of the subject invention is that all magnet coil 23 connectionsbe made directly between the adjacent ends of successive magnets whilemaintaining an equal number of turns in all of the coils 23. ample eachcoil 23 is composed of eight turns.

Considering now the coil winding patterns for the four successivemagnets 12, 13, 14 and 15, with the aforementioned requirements in mind,a coil terminal 38 of the solid line circuit 36 is shown at the bottomcoil layer 12c of the upper pole of first focussing magnet 12. Layer 120is composed solely of four turns of circuit 36 and is coupled at theinnermost turn thereof to the innermost turn of its adjacent top coillayer 12b, the junction point 39 for such inter-layer connectioncorresponding to terminal 31 of FIGURE 3. Circuit 36 continues in thesame direction from junction 39 to form only the main portion of topcoil layer 12b, namely the three innermost turns and an additionalpartialturn through the coil window leg 35 thereof, to an upper coilterminal 41. All turns through the coil window leg 35 of the upper polecoil assembly 23 of the magnet 12 are thus composed of circuit 36. Inthe subassembly structure of FIGURE 3, coil terminal 33 corresponds toterminal 41 of layer 1212.

Referring again to FIGURE 4, the solid line circuit 36 is subsequentlyled to the bottom coil layer 13b on the lower pole of second focussingmagnet 13. The circuit 36 similarly forms the main portion of this coillayer with the additional partial turn thereof along the coil window leg35. The innermost turn of bottom coil layer 13b couples directly to thatof top coil layer 13c, all four turns of which are made of circuit 36. Aterminal 42 brings circuit 36 to the top coil layer 14a of the upperpole of the first defocussing magnet 14, whereupon the current directionthrough the COil Windows is reversed. The four turns of coil layer 14aare composed entirely of circuit 36, and the circuit is coupled directlythrough to all four turns of the adjacent coil layer 14d. From layer14d, the circuit 36 is directed to the lower pole of the same magnet 14,to the bottom coil layer 14b thereof. The circuit 36 forms only apartial turn of this coil layer 14d by passing around the outer legs ofthe winding and avoiding the coil window leg thereof. The circuit 36 iscontinued at the terminal 43 of the top coil layer 15b on the upper poleof second defocussing magnet 15 where it similarly forms only an outerpartial turn of the layer 15b. From layer 155 the circuit 36 is led tothe lower pole of magnet 15 where it forms both coil layers 15d and 15athereof. At coil terminal 53 of the last coil layer 15a, the circuit 36is directed to a similar subsequent sequence of magnets and this In thepresentex- 6 winding pattern is repeated at the corresponding first coilterminal 38 thereof.

The winding pattern of the dashed line, oppositelydirected currentcircuit 37 can be seen in the schematic to be complementary to that ofcircuit 36. Fromthe coil terminal 44 on magnet 15, the circuit 37 formsall of coil layer 15c and forms the major remaining portion of adjacentlayer 15b to a coil terminal 46. Thus the window leg ofthe upper polecoil assembly of magnet 15 contains only this circuit 37. This patternis repeated on the lower pole winding of magnet 14 wherein the coilwindow of this magnet pole is composed of only circuit 37. The circuit37 is continued at terminal 47 to the upper pole of focussing magnet 13where it forms the adjacent coil layers 13a and 13d thereof. The circuit37 is subsequently led to the lower pole of magnet 13 and forms theouter partial turn of the magnet layer 13b. From coil terminal 48 onmagnet 12, the circiut similarly forms a partial turn around the toplayer 12b thereof and then goes to the lower pole of this magnet wherethe circuit forms adjacent coil layers 12d and 12a. From the coilterminal 49 of bottom layer 12a, the circuit is directed to thecorresponding terminal 44 of the second defocussing magnet of apreceding four magnet sequence and the winding pattern is repeatedtherethrough.

In view of the foregoing description, it can be seen that although thetwo winding circuits 36 and 37 are not balanced within a single magnet,they are exactly balanced Within the coil window portions 35 ofthemagnet. The imbalance in the outer region of the winding has only anegligible effect on the beam aperture field. However, this imbalancecondition in turn is staggered from the upper to the lower poles of themagnets and is alternated between the first and second magnets of thetwo magnet pairs in such a way as to cancel out within the totalaccelerator ring.

By Virtue of the systematic distribution of the two circuit 36 and 37combinations among the four magnet positions, it can further be seenthat the total winding pattern essentially constitutes a geometricalarrangement of four basic coil layer types a, b, c and d. Each layertype a, b, c and d is distinguished by the kind and the placement of theterminals thereon and by the presence or absence of a partial turnfeed-through member. All the layer types are included in each of thefour magnet windings, but the physical orientations of each type areeither mirrored or reversed among the four magnets.

Thus, for example, coil layer type b is seen to be the subassemblystructure shown in FIGURE 3. Only layer type b has the outer partialturn feed-through member, the terminal 30 of which in FIGURE 3corresponds to the solid dot type'connection in the schematic FIGURE 4for coupling to the layer type d or" the-same magnet. The opposite legof the feed-through member extends further out from the winding and theterminal 34 thereat is of the open dot type for coupling to an adjacentmagnet. The insulation 28 between the feed-through member and theneighboring turn is slightly increased to better isolate the twocircuits appearing in layer b. The orientation of coil layer b shown inFIGURE 3 is the position it would have as used on magnet 14. On magnet13 the position is rotated about a vertical axis; on magnet 15 theposition is rotated about a horizontal axis; and on magnet 12 theposition is rotated about both axes. It should be noted that the layertype b always occurs as an outside layer on the magnet poles to furtherdiminish the possible effects of the partial turn imbalance. Similarly,layer type a is consistently used in the outside position and types aand d, and b and c are consistently paired on the magnet poles.

The four coil layer types a, b, c and d are thus fabricated according totheir respective winding forms to provide four. corresponding types ofcoil layer subassemblies 24. The subassemblies are arranged in theproper orientations and the paired combinations thereof are assembled onthe magnet core 19 to form the coils 23 on the upper and lower magnetpoles. As can be seen in FIGURE 1, two connecting terminals for the twocircuits 36 and 37 of the coil assemblies 23 appear at both ends of eachgradient magnet and coupling between successive magnets is made directlybetween the adjacent ends thereof. In accordance with the schematic ofFIGURE 4, between like magnets both terminals occur on either the upperor the lower pole coil assembly 23. (Only the upper pole terminals areindicated in FIGURE 1.) Between unlike magnets one terminal occurs oneach of the coil assembies 23. Two short coupling bars 51 appropriatelyinterconnect the coils 23 of the like magnet pairs 12 and 13, and 14 and15, and two longer coupling bars 52 interconnect the coils between thefocussing and defooussing magnet sections where the magnet position isreversed on the accelerator ring 11.

By eliminating the external bus bar connections running throughout thelength of the entire accelerator magnet, as would be required withconventional coil winding techniques, the cost analysis of the 200 bev.accelerator for which the subject invention was designed indicates asavings of $200,000 in conductor material and $300,000 in acceleratortunnel space.

The above description has pertained to a particular accelerator design,however, it can be seen that other combinations of the two-circuitpartial-turn winding technique are possible and would maintain therequired symmetry of thewinding pattern. The concept is equallyapplicable to the excitation coils of other alternating gradient magnetsystem and combinations of magnets as well as to other magnet types,such as quadrupole and sextupole magnets.

Accordingly, it will be apparent to those skilled in the art that whilethe invention has been described with respect to a particular embodimentthereof, numerous variations and modifications are possible within thespirit and scope of the invention and thus it is not intended to limitthe invention except as defined in the following claims.

What is claimed is:

1. In combination wit-h a plurality of magnets which are to be equallyenergized and each of which has a pair of spaced apart poles, a windingfor each of said magnets comprising a first length of conductorextending from a first to a second end of said magnet and having atleast one complete turn and one incomplete turn wound around a polethereof in a first rotational sense, a second length of conductorextending from said first to said second end of said magnet and havingan incomplete turn wound around said pole of said magnet in an oppositerotational sense, which incomplete turn is the complement of saidincomplete turn of said first conductor thereon, and terminal means forconnecting said first and said second lengths of conductor to thesimilar conductors of a preceding and a subsequent magnet at said firstand second ends of said magnet.

2. In a charged particle accelerator of the class having a plurality ofdiscrete magnet sections defining a charged particle orbit, each of saidmagnet sections having a pair of spaced apart poles which are elongatedin the direction of said orbit, a winding for each of said magnetsections comprising a first length of conductor extending from a firstto a second end of said magnet section and having at least one completeturn and one incomplete turn wound around a pole of said magnet sectionin a first rotational sense, a second length of conductor extendingf-romsaid first to said second end of said magnet section and having anincomplete turn wound around said pole of said magnet section in anopposite rotational sense, which incomplete turn of said secondconductor is the complement of said incomplete turn of said firstconductor thereon, and terminal means for connecting said first and saidsecond lengths of conductor to the similar conductors of a preceding anda subsequent magnet section at said first and second ends of said magnetsection.

3. A charged particle accelerator as described in claim 2, wherein saidterminal means connects said first and said 8 second lengths ofconductor to the second and first lengths of conductor respectively of apreceding and a subsequent magnet section at said first and said secondends of said magnet section.

4. In a charged particle accelerator of the class having a plurality ofdiscrete magnet sections defining the charged particles path of saidaccelerator, each of said magnet sections having a pair of spaced apartpoles which are elongated in the direction of said charged particle pathwith one side of said poles forming a magnet coil window adjacent tosaid particle path, a continuous excitation winding for said pluralityof magnet sections comprising a first plurality of coils disposed onalternate poles of successive ones of said magnet sections, each of saidfirst coils having at least one complete turn and one incomplete turnwound around said pole in a first rotational sense, first coupling meansconnecting the terminal end of each of said first coils to the initialend of the subsequent one of said first coils between successive ones ofsaid plurality of magnet sections, a second plurality of coils disposedon the same poles of said magnet sections as said first coils, saidsecond coils having an incomplete turn wound around said poles in anopposite rotational sense to said first coil thereon which incompleteturn is the complement of that of said first coil, 9. third plurality ofcoils disposed on the opposite poles of said magnet sections from saidfirst and second coils, each of said third coils having a completenumber of turns wound around said pole in said opposite rotationalsense, second coupling means connecting the terminal end of each of saidthird coils to the initial end of each of said seconds coils at saidfirst end of each of said magnet sections, and third coupling meansconnecting the terminal end of each of said second coils to a subsequentinitial end of the subsequent one of said third coils between successiveones of said magnet sections.

5. A charged particle accelerator as described in claim 4, wherein saidincomplete turn of each of said first coils is wound along the side ofsaid magnet pole which forms magnet coil window.

6. A charged particle accelerator as described in claim 4, wherein saidcomplete number of turns of said third coil in each of said magnetsections is equal to the number of turns formed by said first and saidsecond coils in said magnet section.

7. A magnet excitation winding system using two conducting circuits fora charged particle accelerator of the type having an alternatingsuccession of focussing magnet pairs and defocussing magnet pairsdefining the charged particle path, comprising a first coil type whichfirst coil type includes one of said conducting circuits, and a secondcoil type which second coil type includes both of said conductingcircuits, said first and second coil types being disposed on theseparate poles of each of said magnets and arranged in a symmetricalpattern among the poles of each sequence of focussing and defocussingmagnet pairs in said succession of said focussing and defocussing magnetpairs whereby the occurrence of said two conducting circuits is balancedwithin each of said magnet pairs and whereby the two conducting circuitsof successive ones of said magnets may be coupled at the adjacent magnetends.

8. A magnet excitation winding system as described in claim 7, whereinsaid first coil type contains (N /2) turns of said first conductorinitiating at a first end of said coil and terminating at the oppositeend of said coil, where (N) is a whole number, said first coil type alsocontaining a complementary half-turn of said second conductor, and saidsecond coil type contains (N) turns of said second conductor initiatingand terminating at a first end of said second coil, one end of saidsecond conductor of said second coil being coupled to the half-turn ofsaid second conductor on said first coil type at said first end of saidcoils.

9. A magnet excitation winding system as described in claim 7, wherein.Said symmetrical pattern of said first and second coil types among thepoles of said sequence of a focussing magnet pair and defocussing magnetpair is characterized by said first and said second coil types beingseparately disposed on the alternate poles of the alternate magnetswithin said focussing magnet pair, the 10ngi- 5 tudinal orientation ofsaid first and second coil types on the second focussing magnet of saidpair being the mirror image of those on said first focussing magnet ofsaid pair, and the disposition of said first and second coil types andthe respective longitudinal orientations thereof within said defocussingmagnet pair being the mirror image of that of said first and second coiltypes Within said focussing magnet pair.

No references cited.

BERNARD A. GILHEANY, Primary Examiner.

G. HARRIS, Assistant Examiner.

1. IN COMBINATION WITH A PLURALITY OF MAGNETS WHICH ARE TO BE EQUALLYENERGIZED AND EACH OF WHICH HAS A PAIR OF SPACED APART POLES, A WINDINGFOR EACH OF SAID MAGNETS COMPRISING A FIRST LENGTH OF CONDUCTOREXTENDING FROM A FIRST TO A SECOND END OF SAID MAGNET AND HAVING ATLEAST ONE COMPLETE TURN AND ONE INCOMPLETE TURN WOUND AROUND A POLETHEREOF IN A FIRST ROTATIONAL SENSE, A SECOND LENGTH OF CONDUCTOREXTENDING FROM SAID FIRST TO SAID SECOND END OF SAID MAGNET AND HAVINGAN INCOMPLETE TURN WOUND AROUND SAID POLE OF SAID MAGNET IN AN OPPOSITEROTATIONAL SENSE, WHICH INCOMPLETE TURN IS THE COMPLEMENT OF SAIDINCOMPLETE TURN OF SAID FIRST CONDUCTOR THEREON, AND TERMINAL MEANS FORCONNECTING SAID FIRST AND SAID SECOND LENGTHS OF CONDUCTOR TO THESIMILAR CONDUCTORS OF A PRECEDING AND A SUBSEQUENT MAGNET AT SAID FIRSTAND SECOND ENDS OF SAID MAGNET.